Some of your Trusted Senders may have more than one email address that they use to send you mail. When a trusted sender is added, we will use the email address that they sent you mail from (if it was created by releasing a message from the Spam section), or the address you sent mail to (if it was created when you sent them a message) or the address you typed in (if you created them yourself.) You can add another address to that trusted sender at any time by going to the Trusted Senders section, selecting their name, and clicking Add to add a new address.
If you don't see an Add button, it's because your trusted sender doesn't have a name associated with their email address. Just change the Name field from the contact's email address to their name, and then you should be able to add a second (or third, etc....) address for that person.